I used to have a Fender
musicmaster bass and as I was getting into jazz fusion in 1990, I decided to get the bass converted to a fretless. I was so excited to get a fretless and I couldn't wait to start making all those "B0aaaawwwwoooong" fretless sounds but I was in for a shock. When I started playing, everything sounded off and out of tune. I'd never played a fretless bass before and as I put my fingers in the places where the notes sounded right, I could see that they bore no relation to where I had been putting them for the previous 8 years ! Sheesh !! So I had to relearn the instrument. I soon lost interest in the fretless and within a couple of years swapped it for an Aria something or other.
Fast forward to 2009 and the idea of the acoustic fretless bass guitar began to seep into my consciousness. I looked them up on ebay and close to where I used to live, this guy that sold beds also sold them in the back of his bedshop ! So I bought one. Cheap as you like. It had fretlines, an inbuilt pick up and a little equaliser and I thought of it as killing two birds with one stone, approximating a double bass as well as fretless electric. It came with roundwound strings and they sounded awfully bright and 'razzy' so I bought a set of flats and got the action changed and pick ups altered. It's nothing like a double bass, by the way !
But I digress.
I find that the fingers need to land just behind the fret lines for the note to be dead on. On the line or in between the lines and the note is off.
I suppose that having lines is cheating

but I don't care. Expertise is not my concern. I just like the sound, want to be in tune and I need the assisstance ! But as I'm playing, looking at the lines is kind of unconscious.